This invention relates to securement of gear members on shaft members in installations such as gear pumps and similar applications involving extreme loads. More particularly, the invention relates to the axial retention or securement of gears on shafts which flex cyclically under vibration and shock loading or other unusually severe operating conditions.
As well appreciated by those skilled in this art, any significant cutting or removal of metal in gear or shaft members increases the likelihood of fatigue failure of the affected member. For this reason, a common method of joining gear and shaft members includes shrink-fitting the gear to the shaft. The latter involves making the internal diameter of the gear slightly smaller than the shaft diameter, and heating the gear to several hundred degrees Fahrenheit. Simultaneously, the shaft is cooled and placed within the bore of the gear. As the temperatures begin to equalize, the swelling of the shaft and the shrinking of the gear will result in the joining of the members wherein the contact zone between shaft and gear will be subject to constant compressive forces.
This particular means has been satisfactory for insuring the radial securement of a gear to a shaft in relatively standard loading environments wherein the significant forces only attempt to force the gear member to rotate relative to the shaft member. However, in gear pump and other environments subjected to severe radial loading, cyclic flexure of the rotating shaft will cause the bore of the gear to bellmouth. The latter phenomenon will often result in axial displacement of the gear along the shaft, causing failure of the gear pump and/or other apparatus.
Notwithstanding the increased likelihood of fatigue failure, conventional means of axial securement of gears on shafts for avoiding the latter displacement under extreme loading have involved keys, pins, snap rings, and other axial holding mechanisms which require localized cutting. The result has been short fatigue life expectancies of gear-shaft systems employed in severe loading environments.